1. Field of the Invention
This invention relates to a magnetic disk cartridge and particularly to a welding pattern of cleaning liners to the inner surfaces of a case.
2. Description of the Prior Art
A conventional welding pattern of cleaning liners in a magnetic disk cartridge will be described with reference to FIGS. 5 to 7.
As shown in FIG. 5, the magnetic disk cartridge includes a case 1 comprising a bottom member 11 and a cover member 12 and a magnetic disk rotatably disposed within the case 1. And liner 2, 2 (cf. FIGS. 6 and 7) for cleaning the surfaces of said magnetic disk are attached to the respective inner surfaces of the bottom member 11 and the cover member 12. The liners 2, 2 are attached to the respective members in the same welding pattern. 4 is a shutter.
The welding pattern of the liners 2, 2 against the respective inner surfaces of the bottom member 11 and the cover member 12 in the conventional magnetic disk cartridge will be concretely described hereinafter. However, as the liner 2 is attached against both members 11 and 12 in the same welding pattern as mentioned above, only the welding pattern of liner 2 against the bottom member 11 will be described and the welding pattern of liner 2 against cover member 12 will be omitted.
As shown in FIGS. 6 and 7, the bottom member 11 is provided with a hub access central opening 11A formed in its center and a transducer (not shown) access rectangular opening 11B formed in adjacent to the central opening 11A.
A liner 2 formed from a nonwoven fabric surrounding the central opening 11A is attached to a part of the inner surface of the bottom member 11 by heating, supersonic wave or the like. The liner 2 is cut out at a portion corresponding to the opening 11B and therefore has a generally C-shaped configuration. The liner 2 has a width enough for cleaning the surface of the magnetic disk. Both the upper and lower surfaces of the magnetic disk are covered with and sandwiched by the liners 2, 2 of the both members. As shown in FIGS. 6 and 7, only the inner surface of the bottom member 11 is attached with the press member 3 formed from a plastic sheet and covered by the liner 2.
The liner 2 has a welding area formed in the vicinity of its edge and partly welded. In the welding area, as is shown in FIG. 6, liner welding portions 2A directing toward the inner side of the liner 2 are formed at a generally equal distance along the edge.
Accordingly, as the liner 2 is welded to the inner surface of the bottom member 11 only at its edge portions, the central portion of the liner 2 is protruded. The magnetic disk contained in the case 1 is cleaned by this protuberance during reproducing and recording.
However, the conventional magnetic disk cartridge has a shortcoming in that the welding area of the liner 2 with respect to the case 1 reaches to an effective magnetic recording area of the magnetic disk and the effect of cleaning is sometimes decreased at this portion. Also, fins are sometimes formed in the welding portion 2A by the welding process. At that time, the effective magnetic recording area is sometimes damaged by contact with the fins. In order to prevent the occurrence of such damage as much a possible, there is a method in which each of the straight lines of the welding portion 2A is made short to form a narrow welding area. However, according to this method, there is such a fear as that the welding strength of the liner 2 with respect to the inner surface of the case 1 is reduced such that the liner 2 is apt to turn up during recording and reproducing of the magnetic disk. When the liner is turned up, the contact resistance between the liner and the magnetic disk becomes large and the rotational torque of the magnetic disk can fluctuate. In some instances, the liner 2 is fluffed due to friction between the liner 2 and the magnetic disk and fibers of the liner 2, i.e., nonwoven fiber fall out and stick to the surface of the magnetic disk. This causes a bad effect on the magnetic disk during recording and reproducing.